Apparatus for coating articles



April 5, 1966 GOODWIN ETAL 3,244,144

APPARATUS FOR COATING ARTICLES Original Filed June 7, 1960 4 se 1 Fig.

INVENTORS MANFRED E. GOODWIN ALEXEY NEKLUDOV ATTORNEY M. E. GOODWIN E APPARATUS FOR comma ARTICLES April 5, 1966 4 Sheets-Sheet 2 Original Filed June 7, 1960 5 m T m V m MANFRED E. GOODWIN ALEXEY NEKLUDOV ATTORNEY April 1966 M. E. eoonwm ETAL 3,244,144

APPARATUS FOR COATING ARTICLES 4 Sheets-Sheet 5 Original Filed June 7, 1960 INVENTORS MAN FRED E. GOODWIN ALEXEY NEKLUDOV ATTORNEY April 5, 1966 o DwlN ET AL 3,244,144

APPARATUS FOR COATING ARTICLES Original Filed June 7, 1960 4 s t s t 4 INVENTORS MANFRED E. GOODWIN I6 B ALEXEY NEKLUDOV ATTORNEY United States Patent 3,244,144 APPARATUS FOR COATlN G ARTICLES Manfred E. Goodwin, liinghamton, N.Y., and Alexey Nekludov, Broornall, Pm, assignors to International Resistance Company, Philadelphia, Pa.

Original application June 7, 1960, Ser. No. 34,414, now Patent No. 3,111,642, dated Nov. 15 1963. Divided and this application Mar. 8, 1%3, Ser. No. 264,485

Claims. (G1. 118-312) This is a division of our co-pending application, Serial No. 34,414, filed June 7, 1960, now Patent No. 3,111,642, issued November 19, 1963, entitled, Electrical Resistor.

The present invention relates to an apparatus for coating articles, and more particularly to an apparatus for coating electrical components with an insulating jacket of a plastic material.

Many electrical components, such as resistors, require a protective coating of an electrical insulating material, such as a plastic. The protective coating mechanically protects the component from being damaged, and electrically insulates the active element of the component from other components in the electrical circuit in which the component is used. The electrical properties of many electrical components, particularly resistors, are often adversely affected when the component is exposed to the atmosphere, and particularly when exposed to the moisture in the atmosphere. Therefore, the protective coating should serve the additional purpose of protecting the active element of the component from the atmosphere, and particularly the moisture in the atmosphere.

A common method heretofore used for applying a protective coating of an insulating plastic around an elec trical component is to coat the component with a liquid plastic either by spraying, painting or dipping, and then curing the plastic layer. However, it has been found that such a protective coating is not sufliciently impervious to the atmosphere to provide the desired protection, particularly when the component is operating at high temperatures. This was found to be true even when the component was provided with a multiple number of coatings of the plastic. In addition, it has been found that such coatings often do not provide the desired electrical insulation since the relatively thin coatings may break down electrically when a load is applied to the component.

Another method of applying a protective plastic jacket around an electrical component is to mold the jacket around the component either by compression or injection molding techniques. It has been found that such a molded protective jacket provides greater electrical insulation for the component as well as better protection against moisture and other contaminants in the atmosphere which may adversely affect the properties of the component. However, the molded protective jacket which will provide such improved protection is much thicker than the coating of the liquid plastic, and thereby substantially increase the physical size of thecomponent. The modern trend in the electronic field is toward miniaturization of electronic equipment and the components used in such equipment. Therefore, the increase in size provided by the molded protective jacket makes such a protection undesirable.

It is an object of the present invention to provide a novel apparatus for coating electrical components with a plastic protective jacket.

It is a further object of the present invention to provide a novel apparatus for continuously coating electrical components with a protective plastic jacket.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention, is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a top plan view of the apparatus of the present invention.

FIGURE 2 is a front plan view of the apparatus of the present invention.

FIGURE 3 is a side view of the apparatus of the present invention taken along line 33 of FIGURE 1.

FIGURE 4 is a sectional view of the front end of the plastic applicator, and the conveyor for the electrical components of the apparatus of the present invention.

FIGURE 5 is a view taken along line 55 of FIG- URE 3.

FIGURE 6 is a sectional view taken along line 6-6 of FIGURE 3.

FIGURE 7 is a top elevational view of the conveyor rack shielding means of the apparatus of the present invention.

FIGURE 8 is a sectional view taken along 8-8 of FIGURE 7.

FIGURE 9 is a perspective view of a rack for carrying electrical components through the apparatus of the present invention.

Referring initially to FIGURES 1 and 2 of the drawing, the coating apparatus of the present invention is generally designated as 10.

Coating apparatus 10 comprises an upright base 12. The top of the base 12 comprises a pair of elongated, horizontal plates 14 and 16. The plates 14 and 16 are in the same plane, and are in spaced parallel relation so as to provide an open space between the inner edges of the plates. Track rails 18 and 20 are mounted on the top surfaces of the plates 14 and 16 respectively, and extend along the adjacent inner edges of the plates 14 and 16 (see FIGURE 4). The track rails 18 and 20 are adapted to slidingly support a rack 22 which carries the electrical components 24 through the coating apparatus 10. A guide rail 26 is mounted on the top of the plate 14. The guide rail 26 extends along and is adjacent to the track rail 18. Guide rail 26 is of a vertical height greater than the height of the track rail 18, and is adapted to engage the outer side of a side flange 28 of the rack 22 to guide the rack along thetra ck rails 18 and 20.

A chain rail 30 is mounted on the top surface of the plate 16. The chain rail 30 extends along and is adjacent to the track rail 20. The chain rail 30 slidingly supports an endless drive chain 32, and guides the drive chain 32 along the upper surface of the plate 16 from one end of the track rail 20 to substantially the other end thereof. As shown in FIGURE 2, the drive chain 32 extends around a pair of guide wheels 34 and 36 which are rotatably mounted on the base 12 at opposite ends of the track rail 20. The guide wheels 34 and 36 are mounted on the base 12 adjacent the top plate 16, and project upwardly above the top surface of the top plate 16 through notches 38 and 40 respectively (see FIGURE 1) in the top plate 16. Thus, the guide wheels 34 and 36 guide the drive chain 32 to a level to permit the drive chain to pass along the chain rail 30. The drive chain 32 is driven by a drive sprocket wheel 42 rotatably mounted on the bottom of the base 12. The drive sprocket wheel 42 is driven by an electric motor 44 through a variable speed transmission 46. The drive chain 32 has a plurality of drive pins 48 (see FIGURE 4) extending therefrom and projecting over the track rail 20. The drive pins 48 are spaced along the drive chain 32, and are adapted to engage an end of a side flange 28' of the racks 22 to move the racks along the track rails 18 and 2t A coating plastic feeder 50 is mounted on the base 12 substantially perpendicular to the track rails 18 and 20, and substantially intermediate the ends of the track rails. As shown in FIGURE 3, the coating material feeder 50 comprises a horizontal tray 52 mounted on a vibrating evice 54. The vibrating device 54 is of any well known type which will vibrate the tray 52 to feed the plastic particles from the back end of the tray to the front end thereof. The tray 52 comprises a horizontally extending bottom 56, a pair of upright side walls 58, a rear wall 69, and an upright front wall 62. As shown in FIGURE 4-, the bottom 56 of the tray 52 has an opening 64 therethrough adjacent the front wall 62. A screen 66 extends across the opening 64, and is mounted in a frame 68 which is secured to the bottom surface of the bottom 56 by screws 70. A pair of battle plates 72 are secured to the front and back sides of the frame 68. The baffle plates '72 extend downwardly from the frame 68 and toward each other to form a funnel for the coating plastic particles which pass downwardly through the opening 64 in the bottom 56 and the screen 66.

The feeder 50 is mounted on the base 12 so that the front end of the tray 52 extends across the track rails 18 and 2t), and the opening 64 in the bottom of the tray 52 is over the space between the top plates 14 and 16. As shown in FIGURES 3 and 4, the bafile plates 72 are angles so that they funnel the plastic coating particles from the tray 52 onto only the body portions 74 of the electrical components 24 that are carried by the racks 22 under the feeder 59.

The feeder 50 is provided with a plastic particle return, generally designated as 76, which catches any of the excess plastic particles and returns the plastic particles to the tray 52 of the feeder 50 for reuse. The return 76 comprises a substantially fiat supporting plate 78 mounted upright on the base 12 behind the feeder 50. The supporting plate 78 has a pair of vertically spaced parallel arms 80 and 82 extending horizontally from its front edge. The top arm 80 of the supporting plate 78 extends over the back end of the tray 52 of the feeder 50. The bottom arm 82 of the supporting plate 78 extends under the feeder 50, and under the top plates 14 and 16 of the base 12. The supporting plate 78 is slidably mounted on the base 12 between guides 84 so that the return 76 can be moved toward or away from the feeder 50.

A pair of identical guides 86 and 86 are mounted adjacent the ends of the arms 80 and 82 respectively of the support plate 78. As shown in FIGURE 6, the guide 86 comprises a wheel 88 having a cylindrical outer surface. The wheel 88 is mounted on a spindle 90 which extends horizontally from and is supported on the arm 80 of the support plate 78. A pair of guide wheels 92 and 94 are rotatably supported adjacent the back end of the supporting plate 78. The guide wheel 92 is in substantial horizontal alignment with the guide 86 on the arm 80, and the guide wheel 94 is in substantial horizontal alignment with the guide 86 on the arm 82. The outer surfaces of the guide wheels 92 and 94 are each provided with a semi-cylindrical groove therearound. A drive and guide pulley 96 is rotatably mounted on the supporting plate 78 between the guide wheels 92 and 94, and the guides 86 and 86. The pulley 96 is of a diameter and is positioned on the supporting plate '78 so that the uppermost point on the pulley is substantially in horizontal alignment with the bottommost point of the wheel 88 of the guide 86, and the bottommost point of the pulley 96 is substant-ially in horizontal alignment with the uppermost point of the wheel 88 of guide 86. The outer surface of the pulley 96 is provided with a semi-cylindrical groove therearound. The pulley 96 is rotated by an electric motor 98 through a variable speed transmission 100.

An endless conveyor 102 extends around the pulley 96, the wheels 88 and 88' of the guides 86 and 86, and the guide wheels 92 and 94. As shown in FIGURE 5, the

conveyor 102 is a hollow, tubular belt of circular transverse cross-section. The conveyor belt 102 is of a relatively rigid but flexible material, such as reinforced rubber, so that the conveyor belt will maintain its tubular cross-section, but will bend around the pulley 96, the guide wheels 92 and 94, and the wheels 88 and 68. The conveyor belt 162 extends around the back portions of the pulley 96 and the guide Wheels 92 and 94 within the grooves in the surfaces thereof, and extends around the front portions of the wheels 88 and 88 of the guides 86 and 86. As shown in FIGURE 5, the wall of the conveyor belt 102 has a radial slit 104 therethrough which extends along the entire length of the conveyor belt. The slot 104 is positioned around the circumference of the belt 162 so that the slit 10-1 is away from the outer surface of the guide wheels 92 and 94 when the belt 192 passes around the guide wheels, and the slit 194- is against the outer surface of the the pulley 96 when the conveyor belt 102 passes around the pulley. As shown in FIGURES 3 and 6, the slit 104 in the conveyor belt 162 permits the tubular wall of the conveyor belt to flatten out when the conveyor belt passes around the cylindrical surfaces of the wheels 88 and 88 of the guides 86 and 86'. However, the resiliency of the conveyor belt 1112 causes the wall of the belt to return to its normal tubular form when the conveyor belt passes away from the wheels 88 and 88. Thus, each of the wheels 88 and 88' causes the conveyor belt 102 to open up as the belt then passes around the wheel, and the belt recloses after it passes from the wheels. The pulley 96 is rotated in the direction of the arrow 166 in FIGURE 3 so that the conveyor belt 102 closes as it moves from the wheel 38 to the pulley 96, and opens as the belt moves toward the wheel 38 from the pulley 96. The conveyor belt 102 is under suflicient tension so that the belt engages the outer surface of the pulley 96 with sufficient force to provide a frictional drive between the pulley and the belt.

For reasons which will be explained later, the conveyor belt 102 should not open up after leaving the pulley 96 until the belt is over the tray 52 of the feeder 5G, or the catch plate 198 extending from the back end of the tray 58 toward the pulley 96. To prevent the conveyor belt 102 from opening too soon, a retainer device, generally designated as 110, is mounted on the supporting plate 78, and engages the belt at a point just beyond the pulley 96. As shown in FIGURE 5, the retainer device 116 comprises a mounting plate 112 secured to the supporting plate 78, and extending over the conveyor belt 162. A roller 114 is rotatably mounted on the mounting plate 112 above the conveyor belt 1132 and engages the top of the conveyor belt. A pair of arms 116 and 118 are mounted on the mounting plate 112 at opposite sides of the conveyor belt 102. The arms 116 and 118 extend downwardly from the mounting plate 112 at an angle toward the conveyor belt 102. Rollers 126 and 122 are rotatably mounted on the ends of the arms 116 and 118 respectively. The rollers 121) and 122 engage the conveyor belt 102 at opposite sides of and adjacent to the slit 104 in the conveyor belt. The points of contact between the rollers 114, 120, and 122 and the conveyor belt 162 are the apices of a triangle which is within the circular crosssection of the conveyor belt. Thus, as the conveyor belt 102 passes between the rollers 114, 1219 and 122, the rollers engage the conveyor belt to support the conveyor belt and maintain the belt closed.

As shown in FIGURE 2, a pair of pre-heaters 124 and 126 are mounted above and below the top plates 14 and 16 of the base 12. The heaters 124 and 126 extend along a portion of the track rails 18 and 20 up to one side of the feeder 50. A post-heater 128 is mounted above the top plates 14 and 16. The post-heater 128 extends along a portion of the track rails 18 and 20 away from the other side of the feeder 50. The heaters 12 126 and 128 may be any type of heater, such as an electrical resistance heater mounted in a reflector casing to direct the heat against the electrical components 24 passing along the track rails 18 and 20.

Rotators 130 and 130 are mounted on the top plates 14 and 16 respectively adjacent the front end of the feeder tray 52 to rotate the electrical components 24 as they pass under the feeder tray. Rotator 130 comprises an upright post 132 mounted on the top plate 14 adjacent the side of the guide rail 26 away from the track rail 18. A plate 134 is pivotally mounted on the post 132 and extends substantially horizontally over the guide rail 26 and the track rail 1.8 beyond the inner edge of the top plate 14. A strip 136 of a friction material, such as felt or rubber, is secured to the bottom surface of the plate 134 adjacent the end of the plate away from the post 132. The friction strip 136 extends along the plate 134 parallel to the path of travel of the rack 22 along the track rails 18 and 20. The friction strip 136 extends from the plate 134 a distance to engage the terminal wires 138 extending from one end of the body portions 74 of the electrical components 24. A guide strip 140 is mounted on the plate 134 and extends along the bottom surface of the plate. The guide strip 140 is spaced from and parallel to the friction strip 136, and is adapted to slidably engage the ends of the terminal wires 138. The rotator 130 like the rotator 130 comprises a post 132 mounted on the top plate 16, a plate 134' pivotally mounted on the post 132' and extending horizontally over the track rail 20 beyond the inner edge of the top plate 16, a friction strip 136 secured to and extending along the bottom surface of the plate 134 adjacent the end of the plate away from the post 132', and a guide strip 140' mounted on and extending along the bottom surface of the plate 134' spaced from and parallel to the friction strip 136'. The friction strip 136' engages the terminal wires 138' extending from the other end of the body portions 74 of the electrical components 24, and the guide strip 140' slidably engages the ends of the terminal wires 138'. As the rack 22 carries the electrical components 24 under the plates 134 and 134', the frictional engagement of the friction strips 136 and 136 with the terminal wires 138 and 138' causes the electrical components 24 to rotate about their longitudinal axes. The guide strips 140 and 140' are positioned to center the electrical components 24 so that the body portions 74 of the electrical components pass under the space between the ends of the bafifle plates 72 of the feeder 50.

Additional rotators 130a, 130b, 1300, and 130d, which are similar to the rotator 130, are mounted in alignment along the top plate 14 beneath the post-heater 128 (see FIGURES l and 2). Also, additional rotators 130a, 1311b, 1311c and 130d which are similar to the rotator 130, are mounted in alignment along the top plate 16 under the post-heater 128. Each of these additional rotators has a friction strip which engages the terminal wires 138 and 138' of the components 24 to rotate the components as they pass under the post-heater 128.

Referring to FIGURE 9, each of the'racks 22 for carrying the electrical components along the coating apparatus of the present invention comprises a pair of spaced, flat end plates 142 extending between and connecting the ends of the upright side flanges 28 and 28'. A pair of U-shaped supporting strips 144 extend between and are mounted on the end plates 142 with the legs 146 of the supporting strips extending upwardly away from the end plates 142. The supporting strips 144 are in spaced, parallel relation, and are spaced from and parallel to the side flanges 28 and 28'. As shown in FIGURE 4, the supporting strips 144 are spaced apart a distance greater than the spacing between each of the supporting strips and its adjacent side flange. The upright legs 146 of the supporting strips 144 are provided with a plurality of aligned slots 148 therein which are uniformly spaced along the portion of the supporting strips 144 'the tracks 18 and 20.

6 which is between the end plates 142. The aligned slots 148 in the legs 146 of the supporting strips 144 receive the terminal wires 138 and 133' of the electrical components 24 so as to support the electrical components 24 in spaced, parallel relation by their terminal wires.

To prevent the end plates 142 of the racks 22 from being coated with the plastic coating material, the apparatus 10 of the present invention is provided with the shielding means shown in FIGURES 7 and 8. The shielding means includes a pair of shielding plates 150 secured in spaced relation to an endless chain 152. The endless chain 152 is mounted on a panel 154 which is secured to the top plate 14 in alignment with the feeder 50. The endless chain 152 is mounted on a pair of sprocket wheels 156 and a drive sprocket wheel 158 for travel in a plane which is parallel to the plane of the panel 154. The sprocket wheels 156 are each rotatably mounted on a separate upright shaft 160, which shafts are mounted on the top plate 14 adjacent the track 18. The drive sprocket wheel 158 is mounted on a vertical shaft 162 which is rotatably supported on the panel 154 behind the sprocket wheels 156, and on a line extending intermediate the sprocket wheels 156. The shaft 162 is drivingly connected through a shaft 164 to a sprocket wheel 166. As shown in FIGURE 2, the sprocket wheel 166 is drivingly connected through an endless chain 168 to a sprocket wheel 170 which is driven by the motor 44 through the variable speed transmission 46. Thus, the endless chain 152 is driven by the electric motor 44 in synchronism with the drive chain 32 for the racks 22.

The shielding plates 150 are mounted in spaced relation on the chain 152 so that the shielding plates 150 extend outwardly from the chain. Thus, when the portion of the chain 152 travels between the sprocket wheels 156, the shielding plates 15% extend across the space between The shielding plates 150 are spaced apart a distance equal to the spacing between the back end plate 142 of a rack 22 and the front end plate 142 of the next rack 22. The chain 152 is of a length so that when the shielding plates 150 reach the position over the racks 22, the shielding plates will each be positioned over an end plate 142 of an adjacent rack 22. The chain 152 travels at the same speed as the chain 32 which drives the racks 22. Thus, the shielding plates 150 travel at the same speed as the end plates 142 of the racks 22 so that the shielding plates will cover the end plates as the end plates travel beneath the coating material feeder 50.

During the time that the shielding plates 150 are over the racks 22, the free ends of the shielding plates are slidably supported on a substantially U-shaped rail 172. The ends of the rail 172 are mounted on the panel 154 at opposite sides of the endless chain 152. The rail 172 projects over the space between the track rails 18 and 20, and the base of the rail 172 is straight and parallel with the portion of the endless chain 152 between the sprocket wheels 156. Posts 174 support the base of the rail 172 on the top plate 16. The inner edge of the rail 172 has a track 176 on which the free ends of the shielding plates 150 are slidingly supported. Thus, the shielding plates 150 are supported from being bent downwardly against the racks 22 by the weight of the coating material which will fall onto the shielding plates.

The coating apparatus 10 of the present invention operates as follows:

A rack 22 is loaded with the electrical components 24 by mounting the terminal wires 138 and 138' of the components in the slots 148 in the legs of the U-shaped supporting strips 144. The loaded rack 22 is then seated on the track rails 18 and 20 at the end of the top plates 14 and 16 adjacent the pre-heaters 124 and 126. The drive chain 32 is driven by the motor 44 in the direction of arrow 178 in FIGURE 2 so that a drive pin 48 on the chain 32 will engage the back end of the side flange 28 of the rack 22 and thereby move the rack along the track rails 18 and 20 toward the feeder 58. As the rack 22 is moved along the track rails 18 and 20 by the drive chain 32, the guide rail 26 prevents the rack from sliding laterally olf of the track rails.

The traversal of the rack 22 along the track rails 18 and 20 carries the electrical components 24 between the pro-heaters 124 and 126 which heat the body portions 74 of the components 24 to the coating temperature. The coating temperature to which the components 24 are heated is that temperature which is suflicient to melt the particles of the coating material when the particles contact the body portions 74 of the components. Thus, the particular coating temperature to which the components 24 must be heated depends on the particular composition of the coating plastic. When coating the components 24 with a silicone resin, it has been found that by heating the components to a temperature of between 250 F. to 350 F. for a period of to 30 seconds, a good coating of the plastic can be achieved. Since the pre-heaters 124 and 126 are both above and below the components 24, the entire outer surface of the body portions 74 .of the components is heated to the coating temperature.

When the rack 22 is started in its travel along the track rails 18 and 20, the vibrator 54 of the coating material feeder 50 is turned on to vibrate the tray 52, and thereby feed the particles of the coating material to the front end of the tray 52. Also, the motor 98 of the coating material return 76 is turned on to move the conveyor belt 162 in the direction of arrow 1% in FIGURE 3. When the coating material reaches the front end of the tray 52 of the feeder 50, the powdered coating material drops through the opening 64 in the bottom 56 of the tray 52, and passes through the screen 66. Thus, a dense shower of the coating material particles is formed in the path of travel of the rack 22. The baffles 72 on the bottom of the tray 52 guide the coating material particles so that the shower of the coating material is contained in a space directly in the path of the body portions 74 of the electrical components 24. The baflles 72 are angled so that the width of the shower of the coating material particles is slightly greater than the length of the body portions 74 of the components.

The travel of the rack 22 along the track rails 18 and 20 carries the electrical components 24, which are heated to the coating temperature, directly from between the preheaters 124 and 126 through the shower of the coating 1 material particles falling from the tray 52. The particles of the coating plastic which contact the heated body portions 74 of the components 24 are heated by the body portions 74, and fuse to the body portions. When the electrical components 24 reach the shower of the coating material, the terminal wires 138 and 138' of the components are carried under and engage the friction strips 136 and 136' of the rotators 130 and 130. The frictional engagement between the friction strips 136 and .136, and the terminal wires 138 and 138 causes rotation of the electrical components 24 as the components are carried along by the racks 22. Thus, as the body portions 74 of the components 24 pass through the shower of the coating material, the body portions 74 are rotated to expose the entire outer surface of the body portions to the shower of the coating material. Since the terminal wires 138 and 138 are small in diameter, the body portions 74 are rotated through a plurality of complete revolutions during the time that the body portions pass through the shower of the coating material. Thus, the body portions 74 of the electrical components 24 are each provided with a coating of the coating plastic which is of uniform thickness around the entire circumference of the body portions. The thickness of the coating provided on the body portions of the components is dependent on the speed of the components through the shower of the coating material particles.

The rack 22 then carries the coated components 24 under the post-heater 128, which re-heats the components. During the passage of the components 24 under the post-heater 128, the components are heated to a temperature of from 250 F. to 350 F. for a period of 5 to 30 seconds. The post-heating of the coated components is to insure complete fusion of the coating plastic. However, the post-heating of the components may be eliminated if the fusion temperature of the particular coating material used is low enough so that the pre-heating of the components achieves complete fusion of the coating material. As the components 24 are carried under the post-heater 128, the additional rotators rotate the components to achieve uniform heating of the components. When the rack 22 of the coated components 24 reaches the end of the coating apparatus 10, the rack 22 is removed and placed in an oven to complete the curing of the plastic coatings.

During the operation of the coating apparatus 10 of the present invention, any of the coating material particles which does not contact the body portion 74 of an electrical component 24 falls through the rack 22, the space between the top plates 14 and 16, and lands on the open portion of the conveyor belt 102 of the return 76 which is beneath the top plates 14 and 16. As the conveyor belt 102 moves along, the wall of the conveyor belt curls around the coating material particles, and carries the coating material around the drive pulley 96 to the wheel 88 above the tray 52. When the conveyor belt 102 reaches the wheel 83, the conveyor belt reopens and drops the coating material particles contained therein back into the tray 52 of the feeder 50. Thus, the unused coating material particles are returned to the tray 5'2 of the feeder 50 for reuse. The retainer of the return 76 prevents the conveyor belt 102 from opening too soon to insure that the coating material particles are properly redeposited into the tray 52. By returning the unused coating material particles back to the feeder 50', any loss of the coating material particles is maintained at a minimum.

Also, during the operation of the coating apparatus 10, just as the end plates 142 of the rack 22 reach the shower of the coating material particles, a shielding plate reaches its position over the end plate 142, and travels over the end plate through the shower of the coating material. Since the end plates 142 of the rack 22 are heated by the pre-heaters 124 and 126, any coating material particles which would fall onto the end plates would fuse to the end plates. However, the shielding plates 15d shield the heated end plates 142 so that little, if any, of the coating material contacts the heated end plates. Since the shielding plates 150 are not heated, the coating material particles which fall onto the shielding plates can be easily brushed therefrom. Thus, the shielding plates 150 prevent any waste of the coating material which may fuse to the end plates 142 of the rack22.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

We claim:

1. Apparatus for coating electrical components of the type having a central body portion and terminal wires extending from opposite ends of said body portion with a protective plastic jacket comprising a base, a pair of spaced, parallel track rails mounted in and extending horizontally along said base, means for driving a rack which contains the components along said rails, heater means mounted along said rails and heating the components, a tray mounted above said base and adjacent an end of said heater means, the front end of said tray extending over said rails, an opening in the bottom of said tray adjacent the front end thereof, means for vibrating said tray to feed plastic particles to the opening in said tray, to form a shower of the plastic particles in the path of travel of said components, and means mounted along each of said rails for engaging and rotating the components as the rack passes under the tray.

2. The apparatus in accordance with claim 1 in which the base has an opening therethrough between the rails and under the opening in the tray, and means beneath said rails for catching any of the plastic particles passing through the opening between the rails and returning said plastic particles to said tray.

3. The apparatus in accordance with claim 2 in which the means for catching and returning the plastic particles includes a flexible endless belt of tubular transverse crosssection, said belt being mounted for travel in a path which extends from beneath said rails to above said tray, said belt having a slit therethrough which extends along the entire length of the belt, and means positioned along the path of travel of said belt below the rails and above the tray for flattening said belt.

4. Apparatus in accordance with claim 3 in which each of the means for flattening the belt comprises a wheel having a cylindrical outer surface about which the belt extends.

5. Apparatus in accordance with claim 1 including an additional heater above the rails and extending along the rails from the side of the tray opposite the first mentioned heater means, and means mounted along the rails beneath said additional heater for engaging and rotating the components.

References (Iited by the Examiner UNITED STATES PATENTS 1,999,509 4/1935 Merritt 117-21 X 2,264,499 12/1941 Bair 1l8308 X 2,737,461 3/1956 Heisler et al '11721 X 3,016,875 1/1962 Ballentine et a1 117-21 X 3,170,808 2/1965 Almy et al 117-21 X FOREIGN PATENTS 1,000,921 10/1951 France.

DANIEL BLUM, Primary Examiner. 

1. APPARATUS FOR COATING ELECTRICAL COMPONENTS OF THE TYPE HAVING A CENTRAL BODY PORTION AND TERMINAL WIRES EXTENDING FROM OPPOSITE ENDS OF SAID BODY PORTION WITH A PROTECTIVE PLASTIC JACKET COMPRISING A BASE, A PAIR OF SPACED, PARALLEL TRACK RAILS MOUNTED IN AND EXTENDING HORIZONTALLY ALONG SAID BASE, MEANS FOR DRIVING A RACK WHICH CONTAINS THE COMPONENTS ALONG SAID RAILS, HEATER MEANS MOUNTED ALONG SAID RAILS AND HEATING THE COMPONENTS, A TRAY MOUNTED ABOVE SAID BASE AND ADJACENT AN END OF SAID HEATER MEANS, THE FRONT END OF SAID TRAY EXTENDING OVER SAID RAILS, AN OPENING IN THE BOTTOM OF SAID TRAY ADJACENT THE FRONT END THEREOF, MEANS FOR VIBRATING SAID 